1. Field of the Invention
The present invention relates to an information recording medium for recording general data (e.g., programs) and/or real-time data (e.g., video data and/or audio data) thereon on a sector-by-sector basis; a method for recording data on the information recording medium; a method for reproducing data on the information recording medium; and a system controller, an information recording apparatus, and an information reproduction apparatus for performing such methods.
2. Description of the Related Art
Optical disks are representative of information recording media having a sector structure. The recent trend for higher density, larger capacity, and multimedia technologies has shed light on optical disks as information media for use with personal computers and various consumer use apparatuses.
Hereinafter, by referring to the accompanying figures, a DVD-RAM disk will be described as an example of a conventional rewritable optical disk. FIG. 16A illustrates the physical layout of a conventional rewritable optical disk of a ZCLV (zoned constant linear velocity) format.
As shown in FIG. 16A, the rewritable disk includes a lead-in area, a DMA (defect management area), a data area, and a lead-out area, in this order from the inner periphery to the outer periphery. The DMA is used for managing defective sectors on the disk. Each area has digital data recorded therein. The digital data is managed in units which are commonly referred to as sectors. The data area includes a spare area used for replacing a defective sector in a replacement process, as well as regions denoted as zones 0 to 34. In each zone, data is recorded in physical sectors which are 2048 bytes long.
As shown in FIG. 16B, information areas on the rewritable optical disk have physical sector numbers (PSN) assigned thereto. User data may be recorded in a space which is defined as a volume space including logical sectors to which logical sector numbers (LSN) are assigned. Stated otherwise, the volume space is the information area minus the lead-in area, the DMA, the unused regions within the spare area, any number of defective sectors which are registered in a primary defect list (PDL) within the DMA, guard regions in between the respective zones, and the lead out region. In order to provide improved data reliability, an error correction process is performed on an ECC block-by-ECC block basis, where each ECC (error correction code) block is composed of 16 logical sectors.
Any defective sectors which have been detected through a certify process performed at the time of initialization of the disk are registered in the PDL, so that these defective sectors will not receive any LSNs assigned thereto. Therefore, it is possible that sectors of consecutive logical addresses may include regions which are not in a physically consecutive order. Any defective sectors which are detected during data recording are subjected to a linear replacement whereby the entire ECC block containing each defective area is replaced by a spare region, and are registered in a secondary defect list (SDL) within the DMA. Thus, a rewritable disk is provided with a mechanism for improving data reliability.
As described above, a DVD-RAM disk, which is provided with a defect management mechanism, is subjected to a defect management process by a drive. On the other hand, a CD-RW disk which is not provided with any defect management mechanism, is subjected to a defect management process—similar to the aforementioned SDL-based defect management—which is performed by a file system based on a sparing table as defined under the UDF® (universal disk format) specification of OSTA. Specifically, in the case of CD-RW disks, the entire ECC block including a defective sector is replaced by a spare area which is set within the volume space, and this replacement information is managed based on a sparing table as defined under the UDF specification.
Next, as an example of a conventional write-once optical disk, a 3.95 Gbyte DVD-R as specified under the DVD-R Standards (Version 1.0) will be described. It is assumed that the volume/file structures conform to the data structures defined under the ISO/IEC 13346 Standards or the UDF specification, unless otherwise specified.
FIG. 17 illustrates an exemplary directory structure to be recorded on an optical disk. Under a ROOT directory 201 is recorded a REALTIME directory 202, which is dedicated to video applications. Under the REALTIME directory 202, audio/video data (hereinafter referred to as “AV data”) which has been compressed in the MPEG format is recorded in a file named VIDEO.VRO file 203. A number of still picture files which have been recorded by means of a digital camera or the like are recorded in a file named FILEA.DAT 204.
FIGS. 18A to 18C are diagrams illustrating extent locations in the case where AV data is appended to the VIDEO.VRO file. As used herein, an “extent” means a region containing logically contiguous sectors in which data is recorded.
When AV data is recorded, a linking loss area 561 (32 KB) is first recorded, and thereafter AV data is recorded in an extent 562, and furthermore a padding area 563, in which 00h data is recorded, is recorded in the sectors up to the ECC block boundary. In the case of DVD disks, an ECC error correction is performed in units of 16 sectors, so that data recording also occurs in units of 16 sectors. Next, a file structure concerning this DVD-R disk is recorded. After a border-out (not shown) is recorded so as to enable reading by a read-only system, a recording area will be formed after the padding area 563. The border-out has a size of 10 to 100 MB.
In the case of a DVD-R disk in which data is sequentially recorded, AV data will be sequentially appended, beginning from the inner periphery of an unrecorded area which is left in the outer periphery of the disk. Therefore, in a second append operation, as shown in FIG. 18B, after a linking loss area 564, AV data is recorded in an extent 565, and a padding area 566 is recorded in the sectors up to the ECC block boundary.
Similarly, as shown in FIG. 18C, in a third AV data append operation, a linking loss area 567, an extent 568, and a padding area 569 are recorded. Thus, AV data is appended in split portions over a number of extents.
Next, a linking scheme for DVD-R disks will be described with reference to FIGS. 19A to 19D. A so-called “buffer underrun” occurs due to the difference between the data rate of the AV data to be recorded and the data rate when the data is recorded on the disk by the pickup. If a buffer underrun occurs, the drive temporarily suspends the recording, and resumes recording after a predetermined amount of data is stored within the buffer. At this time, the linking scheme forms a linking loss area.
FIG. 19A is a diagram illustrating extent locations in the case where two buffer underruns occur during AV data recording. Extents 222, 223, and 224 represent areas in which AV data has been recorded. A linking loss area 220 is an area which is recorded prior to the recording of AV data. Linking loss areas 226 and 227 are areas which are recorded responsive to the buffer underruns.
FIGS. 19B and 19C are sector-by-sector illustrations of area structures. The linking loss area 220 is recorded by recording 00h data so as to begin in the middle of the first sector and reach the end of the 16th sector. If an ensuing extent 222 is to be recorded, the extent 222 is recorded from the beginning of the first sector up to the beginning in the next sector adjoining this extent, and the recording operation is finished for the time being. Next, when the linking loss area 226 is to be recorded, the recording is resumed in the middle of the first sector. Thus, since a data append operation for DVD-R disks occurs in the middle of a sector, any sector that contains areas which are adjoined by the linking scheme is referred to as a linking sector 225.
The specific linking scheme to be performed within a linking sector is illustrated in FIG. 19D. One sector consists of 26 sync frames. Reference numerals 241, 242, 243, and 244 represent areas which are recorded at an end portion when the extent 222 is recorded; 241 and 242 represent a sync portion and a data portion, respectively, of a first sync frame; and 243 and 244 represent a sync portion and a data portion, respectively, of a second sync frame. The data portions 242 and 244 are sized so as to be able to allow 91 bytes and 86 bytes of data, respectively, to be recorded therein. An area 245 and the following areas represent areas which are formed within the first sector of the ECC block in the linking loss area 226 when the extent 223 is recorded. Reference numeral 245 represents a data portion in the second sync frame. Reference numerals 246 and 247 represent sync portions in sync frames.
Data 00h is recorded in a runout area 228 so as not be finalized at the time of recording the extent 222. A region 229 spanning from the 82nd byte to the 87 bytes in the second sync frame is a region which overwrites a previously recorded area through appending; this area is referred to as a linking gap because no valid data can be recorded therein. Thus, the linking sector 225 containing the linking gap 229 is subject to the physical constraint that data cannot be properly recorded therein. Therefore, the 32 KB ECC block containing this linking sector is defined as a linking loss area so as to ensure that any data that requires reliability is prevented from being recorded therein as valid data.
However, in the case where real-time data is reproduced from an optical disk having the aforementioned format with the real-time data being recorded thereon, it is difficult to continuously reproduce the recorded real-time data because access may have to occur to physically non-contiguous areas which are formed between or within extents.
In particular, in the case where data is recorded in a conventional file system, the data reproduction may be interrupted due to a data read delay occurring when accessing a guard area provided in the vicinity of a zone boundary, a read delay arising from any defective sectors or defective blocks that are registered in the PDL or SDL, and/or a data read delay arising from bouncing from one recording area to another to access data recorded in a plurality of discrete, empty areas.
Since it is currently impossible to distinguish real-time files from general files, once an error occurs during the reproduction of real-time data, a delay may occur in order to again reproduce a location which was not successfully reproduced previously.
Since no identification information is currently available to show conditions for reproducing real-time data and the fact that given real-time data was in fact recorded under such conditions, it is impossible to know whether or not the recorded real-time data can be continuously reproduced.
In the case where a recording apparatus appends real-time data to an already-recorded real-time file, it may not be possible to achieve continuous data reproduction between the end portion of the already-recorded data and the beginning portion of the appended data.
In the case of real-time data which has been encoded by the MPEG method, it may not be possible to achieve continuous data reproduction between the end portion of the already-recorded data and the beginning portion of the appended data due to differing encoding conditions.
In the case of an optical disk to which data is recorded while using a linking scheme, e.g., a DVD-R disk, a linking loss area which is 32 KB long is formed every time a buffer underrun occurs. This causes each area in which data is recorded to be split into a plurality of extents, resulting in a large amount of address information being associated with each extent to be managed by the file system, making it difficult to reproduce the data by means of a reproduction-only apparatus with a limited memory size. Moreover, when AV data having a low data rate is recorded, linking loss areas to be recorded will account for a large proportion, resulting in a poor recording efficiency.